1. Field of the Disclosure
The disclosure relates to a multi-carrier receiver, a multi-carrier transmitter and a multi-carrier transceiver system.
2. Description of Related Art
Currently, wireless broadband communication technology generally uses a carrier aggregation technique to improve a spectrum efficiency of limited frequency resources and enhance data transmission capability. In the carrier aggregation technique, data required to be transmitted is distributed to sub-carriers with relatively smaller bandwidths. Since a present spectrum distribution approach limits availability of a continuously large band, in the carrier aggregation technique, the sub-carriers can be contiguous, non-contiguous or even inter-band allocation.
In an application of the carrier aggregation technique, a radio frequency (RF) transceiver system must simultaneously transmit a plurality of signals, and a common implementation thereof is to use a plurality of RF transceivers, and suitably design a bandwidth required by each RF transceiver. FIG. 1 is a functional block diagram illustrating a conventional multi-carrier receiver 100. For simplicity of illustration, only two analog signal processing paths are schematically illustrated in FIG. 1 for processing signals of two bands and transmitting processed signals to a digital signal processor 150 for further processing. A first analog signal processing path in the multi-carrier receiver 100 receives a RF signal from an antenna, and performs signal gain processing and frequency down-conversion processing to one or a plurality of sub-carrier signals of a first band (band 1) sequentially through an amplifier 110, a mixer 120 and a local oscillator 130. After the sub-carrier signals are down-converted, a filter 142 in an analog signal processing unit 140 filters noises not belonging to a predetermined bandwidth from the sub-carrier signals, and a demodulator 144 demodulates the sub-carrier signals. Then, the demodulated sub-carrier signals are converted into digital signals by an analog-to-digital converter (ADC) 146, and the digital signals are transmitted to the digital signal processor 150 for further processing. Similarly, in a second analog signal processing path of the multi-carrier receiver 100, components such as an amplifier 160, a mixer 170, a local oscillator 180, and a filter 192, a demodulator 194 and an ADC 196 in an analog signal processing unit 190 that are symmetrical to that of the first analog signal processing path are used to process one or a plurality of sub-carrier signals of a second band (band 2) according to the same processing method as described for the first analog signal processing path, and the processed signal is transmitted to the digital signal processor 150 for further processing.
The first and the second analog signal processing paths in the multi-carrier receiver 100 all preserve the maximum bandwidth (for example, the ADCs and the filters) in hardware design. It is noted that a bandwidth requirement of the ADC is not only a sum of bandwidths of all of the sub-carriers, but frequency differences of sub-carrier frequencies are also simultaneously taken into consideration, so that the RF signals can be linearly converted into digital signals, so as to maintain signal qualities of the converted sub-carrier signals. If the frequency differences of the sub-carrier frequencies are relatively greater or in case of the inter-band distribution, channel fading of the sub-carriers are different, so that the ADC is required to have relatively greater dynamic range. However, during practical operations, the received sub-carriers may not be evenly distributed to the two analog signal processing paths, and this situation causes a waste of the hardware circuit and power consumption.
Regarding other techniques for processing multi-carrier signals, the RF signal is generally converted into the digital signal, and then digital filtering processing is performed, so as to implement a multi-carrier transceiver capable of simultaneously processing a plurality of non-contiguous sub-carriers. However, these conventional multi-carrier signal processing methods still require ADCs of high complexity and high hardware cost, and meanwhile bandwidth requirements thereof are also very high. Therefore, in a multi-carrier transceiver capable of simultaneously processing a plurality of non-contiguous sub-carriers, it is an important issue to reduce complexity and hardware cost of the overall multi-carrier transceiver system.